The goal of this research is to increase the comfort of CPAP therapy for middle and upper age obstructive sleep apnea (OSA) patients. The most successful assisting device for treating OSA is the nasal CPAP machine. However, a major problem associated with CPAP therapy is the lack of patient compliance over an extended time period. A principal reason for the lack of long-term patient compliance is the sensation of continuous forced air through the nose and throat. Commercially available CPAP machines apply a constant elevated pressure with no dynamic pressure adjustment. An intelligent control strategy is proposed that lowers the pressure when no obstruction is present and raises it when apnea is about to occur, thus lowering the overall mean pressure to which the patient is exposed. Since obstructive apnea episodes occur only during sleep, the pressure will be elevated only when the patient is asleep. Hence, this will prevent the patient from feeling the high pressure flow. Such improvement will boost the efficacy of CPAP therapy for a large number of patients; it is estimated that 2% of working male adults in the U.S. suffer from OSA.To test the control strategy, a new microprocessor-based CPAP ventilator has been developed; commercial units cannot be programmed to adjust the pressure as desired. Using the new ventilator, the performance of the proposed control strategy will be tested in 30 OSA patients in a fully equipped and accredited sleep laboratory. The focus of the study will be on demonstrating that the new controller can effectively eliminate obstructive sleep apnea. This study will pave the way for clinical investigation of the benefits of the proposed variable positive airway pressure therapy for OSA patients in the future.